This invention relates generally to the field of ceramic coatings and, more specifically, to a method and system for forming a low temperature cured ceramic coating for elevated temperature applications.
Ceramic coatings are often applied to jet engine and exhaust components for thermal protection and energy absorption. Ceramic coatings are often formed by applying water-diluted, cement-based ceramic slurries, followed by ambient environment evaporation of the water of solution and elevated temperature curing of the cement to remove water of hydration. The cements are typically silicates of alkali metals and are used to bind together the appropriate ceramic oxides and energy absorbing fillers. The cements may also function as a primer to adhere the coating to a metallic, ceramic or other substrate.
Most ceramic coatings are cured at temperatures of 1,000xc2x0 Fahrenheit or greater. Ceramic coatings that are applied under normal, ambient conditions and cured at low temperatures tend to crack and fail. Low temperature curable ceramic coatings, with or without a drying control agent, may also crack and fail if applied and cured rapidly.
In accordance with one embodiment of the present invention, a system and method for forming a low temperature cured ceramic coating for elevated temperature environments is provided that substantially eliminates or reduces disadvantages and problems associated with previously developed systems and methods.
In accordance with one embodiment of the present invention, a method for forming an elevated temperature durable coating on a surface of a substrate includes applying an aqueous slurry comprising lithium silicate, sodium silicate, potassium silicate, zirconia powder, a fibrous agent, and a magnetic powder to a surface of a substrate in one or more layers of substantially uniform thickness to form a coating. A substantially controlled humidity environment is maintained during application of the aqueous slurry and the coating is ambient dried for a period. A drying agent is applied to the coating and formation of a dry crust is prevented on the coating during ambient drying. After the period, the coating is heat cured.
In accordance with another embodiment of the present invention, a heat resistant component for high temperature applications includes a coating comprising matrix materials, binder materials, strengthener materials, and magnetic fillers applied in one more substantially uniform thin layers to a component. The coating is applied in a substantially controlled humidity environment and dried for a period between application of each of the one or more thin layers. A drying agent is applied to the coating and the coating and drying agent are heat cured for a period.
Technical advantages of one or more embodiments of the present invention include providing a heat resistant ceramic coating and method for high temperature applications that includes applying an aqueous slurry and a drying agent to the substrate in a substantially controlled humidity environment to form a coating. After application of the aqueous slurry and drying agent, the coating is heat cured. Thus, a more uniformly cured coating with reduced drying stresses is provided.
Another technical advantage of one or more embodiments of the present invention includes providing a heat resistant, erosion resistant, ceramic coating which is substantially less susceptible to blisters, cracking, and shrinkage. More specifically, a ceramic coating is provided that does not develop large cracks and subsequently disbonds from the substrate. Moreover, the resultant coating forms a solid protective layer that is resistant to high humidity degradation or blistering after exposure to temperatures above 1,000xc2x0 Fahrenheit. And longevity of substrates subjected to elevated temperatures is improved, reducing repair and/or replacement costs.
Other technical advantages of one or more embodiments of the present invention include providing a method for forming an elevated temperature durable coating on a surface of a substrate that includes applying an aqueous slurry and a drying agent to form a coating while maintaining a substantially controlled humidity environment during application of the coating. In this way, a low-cost method for providing a durable coating on a surface of a substrate for use in elevated temperature environments is provided that can be applied to ceramic, titanium, and other substrates. The coating is heat cured and the resultant coating provides a moisture-resistant protective coating typically allowing small cracks of less than ten millimeters when exposed to elevated temperature environments, thereby allowing the coating to tolerate strain without disbanding from the substrate.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims. Moreover, some, all, or none of the above technical advantages may be included in the various embodiments of the present invention.